Description: The purpose of this recommended practice is to suggest a set of transmission performance parameters to be used in the development of standards for low bit-rate digital channels between the user's location and an appropriate test point at the serving office. This recommended practice suggests a set of performance parameters for digital loop transmission between the user location and the serving office. In the case of ISDN the user location is defined as the T-reference point, or the U-reference point. In the case of non-ISDN, the user location is defined as the point in the transmission circuit analogous to the ISDN-defined T or U reference point. This recommended practice is limited to user information bit rates of 200 kb/s or lower.